As the feature size of a micro-device such as a semiconductor device shrinks, a technique in a manufacturing process for removing fine foreign substances (particles) by cleaning and preventing the foreign substances from attaching to an object such as a substrate while processing the object has become significant.
In order to solve the problem of the foreign substances, it is required to cause the foreign substances detached from an object to be processed or foreign substances present in a processing liquid to overflow from a processing bath to discharge them outside the processing bath quickly. Generally, an upward injection scheme of injecting the processing liquid from the bottom of the processing bath is considered effective. With this scheme, the flow rate and flow velocity of the processing liquid can be increased.
With the upward injection scheme, however, uniform flow rate and flow velocity of the processing liquid cannot be ensured sufficiently.
Japanese Patent Laid-Open No. 7-161677 discloses a cleaning apparatus in which a rectifier plate having a large number of holes is arranged between a wafer and a supply pipe arranged at the bottom of a cleaning bath. In the apparatus described in this reference, the pressure of a liquid supplied to the wafer through the rectifier plate is not uniformed. In a region where the liquid pressure is high, the wafer vibrates to easily cause friction between the wafer and a carrier. This friction can cause chipping to generate particles. The nonuniform pressure causes turbulent flow of the liquid to interfere with quick discharge of the particles outside the processing bath.
According to Japanese Patent Laid-Open No. 7-297164, a plurality of rectifier plates are arranged to prevent the cleaning liquid from standing or whirling. According to Japanese Patent Laid-Open No. 9-232272, a plurality of rectifier plates are arranged. The higher the position where the rectifier plate is arranged, the smaller the hole diameter of the rectifier plate. The plate thickness of the rectifier plate arranged at the uppermost position is made as large as twice or more the hole diameter of the rectifier plate. Consequently, a laminar flow is formed. In each of the apparatuses described in Japanese Patent Laid-Open Nos. 7-297164 and 9-232272, however, because the size of the processing bath in the depth direction increases, the apparatus size increases, and the quantity of necessary processing liquid increases. This prolongs a time required for changing the processing liquid.
Japanese Patent Laid-Open No. 10-209105 discloses a cleaning apparatus in which a buffer plate is arranged between a rectifier plate and injection port. Even with this method, the same problems as that described above arise.